Snow is typically removed from pavement such as roads, highways, runways, and the like by a truck that includes a snowplow with a moldboard that is mounted on the front end of truck. A variety of arrangements exist for raising and lowering the moldboard, changing the angle the moldboard makes with the longitudinal axis of the truck and with respect to the longitudinal axis of the pavement being cleared. The lowermost edge of the moldboard may contact or be in near contact with the pavement being plowed or may be lifted to be out of contact with the road (e.g., by several inches or feet) so that, for example, pavement already cleared of snow is not again plowed and obstructions may be cleared, such as speed bumps.
Wing portions and other attachments have been used to effectively extend the width of the moldboard to remove more snow from pavement being plowed in a single pass. Front-mounted snowplows can often be angled towards the right or left to push snow to either side of the vehicle via the use of hydraulics. When known snowplows are used on pavement, the plowed snow may be deposited on previously cleared portions of the pavement, particularly in instances where additional plowing of pavement is necessary prior to the melting or removal of previously plowed snow. One mechanism is to provide a towed snowplow, such as described in U.S. Pat. No. 7,367,407 issued to the same assignee, herein incorporated by reference.
On a different note, in conventional steering mechanisms 100, an example of which is shown in FIG. 1, steering geometries are employed to prevent the sideway slippage of wheels when turning. Ackerman steering geometry is one such steering geometry that is commonly employed. Ackerman steering geometry helps prevent the slippage of wheels slipping sideways when turning by having each wheel track an independent pivot that is close to each wheel's hub, as discussed in more detail below. Such geometries, however, may be disadvantageous in instances where the orientation of the vehicle is to remain at an angle, such as in the instance of a towed snowplow being oriented at an angle to push snow towards the outside of pavement. These traditional steering geometries can result in wheel alignment that is out of parallel when angled orientation is used for prolonged periods of time, such as in the case of an engaged snowplow, which can in turn result in uneven tire wear and additional complications. This would be even more true when the conventional mechanism were used to try to move the towed snowplow in either direction, right or left of the vehicle towing the snowplow. Other types of steering geometry are known, but these other types of steering geometry also result in the wheels having alignment that is out of parallel, resulting in uneven tire wear and addition complications when the orientation of the vehicle is to remain at an angle.
Thus, there is a need for a steering mechanism that can compensate for the angled orientation of a vehicle to provide for more properly oriented wheels, thereby reducing tire wear and increasing vehicle performance. Further, it would be advantageous if such a steering mechanism would prevent the towed snow plow from going from one side to the other because of over-steering or the like in that the towed snowplow might inadvertently enter the travel path of oncoming traffic or other obstacles or obstructions.